1. Field of the Invention
The present invention relates to a differential gear employing helical gears and used for a vehicle.
2. Description of Related Art
An example of a differential gear employing helical gears is disclosed in Japanese Unexamined Utility Model Application Publication No. H07-34247.
The differential gear of this disclosure is for a vehicle and has a differential case that supports a pair of helical side gears serving as helical output gears that axially face each other. On the peripheries of the helical side gears, a pair of pinion gears are arranged adjacent to each other in a circumferential direction, the pinion gears meshing with each other. One of the pinion gears meshes with one of the helical side gears and the other of the pinion gears meshes with the other of the helical side gears. Between the helical side gears, a thrust bearing is arranged. This thrust bearing exhibits a bearing function when outward thrusting forces are applied to the helical side gears to push the helical gears toward walls of the differential case.
The thrust bearing can enlarge the difference of differential limiting force between a driving operation and a coasting operation of the vehicle.
This related art, however, must arrange a hub between the helical side gears so that the hub may get in contact with the thrust bearing. This configuration complicates the structure of the differential gear.
According to the related art, the thrust bearing is positioned close to the axial center of the helical side gears. This configuration limits the size of the thrust bearing to be small. Due to the small size, the strength of the thrust bearing is insufficient to realize a structure that can secure a practical difference of differential limiting force between a driving operation and a coasting operation.